36 Trans. Acad. Sci. of St. Louis. 
short copulating period with perfect oviposition, a long 
copulating period with imperfect oviposition, and vice 
versa. 
(d) The relation of the difference in the ages of the par- 
ents at the time of copulation to the number of eggs 
retained at death. 
KNOWN AS DIFFERENCE IN AGE NUMBER OF EGGS 
DAYS HOURS RETAINED 
A 8 25 5:30 older than 98 
A 12 91 15:30 older than § 55 
Al4 20 20 olderthan J 125 
A 15 20 0:20 older than J 0 
A 10 22 0:30 younger than °j 0 
A 9 22 1 younger than ¢ 4 
A 10a 22 0:30 younger than 14 
The figures show that there is a direct relation between 
the ages of the parents at the time of copulation and the 
number of eggs retained at death. In A 15 we have the 
most perfect oviposition, there being only a difference 
of 20 minutes in the ages of the male and female. In A 
10, A 9, and A 10%, we have perfect or almost perfect 
oviposition. In each of these cases it is shown that the 
female was more than two days younger than the male 
at the time of impregnation. In A 8, A 12, and A 14, we 
have very imperfect oviposition, the number of eggs re- 
tained at death being 98, 55, and 125 respectively. In each 
case we find the female older than the male. 
The fact that there is a relation between perfect ovi- 
position and the younger age of the female, and between 
imperfect oviposition and the older age of the female 
ean be accounted for in this way. Hach individual is des- 
tined to live for a certain length of time, females from 
6 to almost 10 days. Where the male is of equal age or 
older than the female we have perfect or almost perfect 
oviposition. To insure the deposition of all the eggs, the 
male, so to speak, must be in readiness, waiting for the 
female to hatch. In the cases where no males were at 
hand when the females had hatched and the females were 
compelled to await impregnation for a certain number of 
their days, which were spent in activity with consequent 
